Air flow interlock



Oct. 14, 1941. J. L. FINCH AIR FLOW INTERLOCK Filed Oct. 22, 1958 2 Sheets-Sheet l INVENTOR mfr/f ATTORNEY f4/77 F BY 7 Z Oct. 14, 1941. J. 1 FlNcH 2,259,104

AIR FLOW INTERLOCK Filed Oct. 22, 1958 2 Sheets-Sheet 2 vill/11111 I I m f-f--f-f--f---w--T------ig TOR INVEN f/7755 L ATTORNEY Patented Oct. 14, 1941 AIR FLOW INTERLOCK James L. Finch, Patchogue, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application October 22, 1938, Serial No. .236,384

14 Claims.

This invention relates to a :new and novel air flow interlock for use in a radio transmitter which is particularly adapted to be responsive to flow of a luid and to .actuate an interlock or indicating device in one direction when the air flow exceeds a predetermined value and in an opposite direction when the airflow is less than a predetermined value. The interlock by means of switch contacts also shuts off the power from the Vvacuum tubes of the transmitter upon a decrease or failure of the cooling fluid.

An object of this invention is to simplify vand improve small air flow interlocks so as toofer a minimum of obstruction to the flow.

Another object of this inveniton is to provide a sensitive device which will be .responsive tothe iiow of the iiuid and so as :to .actuate .an interlock indicating device in one direction when an air flow exceeds a predetermined value and in the opposite direction when the .air flow is :that vof a lesser predetermined value.

Still another object .of :this'invention is to pro- .vide a device which will have .a certain inertia so that quick changes in the flow will .not cause the device to chatter or flutter.

A feature of this invention is the novel arrangement of an air flow interlock which comprises the combination `of a fan, a spring and electrical switch contacts, 4the device A.being arranged so that it may be accurately set so that relatively small changes in fluid can lbe `relied upon to actuate the interlock or indicating device.

Another feature of this invention is Ythat the device is so enclosed that it retains its lubrication throughout a long period of continuous operation and alsol the device is completely enclosed .as to keep out dirt and dust.

This invention will best be understood by referring to the accompanying drawings, in which:

Fig. lis a front elevation;

Fig. 2 is a cross-section ofV Fig. l; Y Fig. 3 is a partial elevation of Figs. V1 and with the cover removed to show-the switch Iactuating mechanism;

Fig. 4 is a partial section of another fan modication;

Fig. 5 is a sectional View of a vacuum tube cooling arrangement, employing the -air flow interlock of this invention; while Fig. 6 is an .elevation of a blower having associated therewith the air flow interlock of this invention.

Referring now Vin detail to Figs. 1, 2 and3, of

CTX

the drawings,l a metallic housing I is arranged 5'5 to support a depending tubular member 2, the bottom portion of which is threaded to receive a bearing 3 for a rotatable shaft 4, shaftv4 isprovided with a high pitch fan 5 with its axis common to that of shaft 4, shaft 4 being arranged essentially parallel to the direction of the fluid iiow. Within the casing I there is provided a second bearing rIi, which is similar to bearing 3 except .that it is threaded with a fine thread 1, a corresponding vthread being' cut inthe upper end of shaft '4, the lower bearing 3 being a normal sleeve bearing, allowing shaft 4 to rotate and to move .endwise or upward Yby means of movement in the upper bearing -6 which is threaded. In other words, the upper end of the shaft is cut with a Very ne thread, for example, forty threads perinch, thus, when the shaft rotates, it is forced to move endwise by these threads. Shaft 4 is surrounded by la helical steel spring 8, the upper end of the spring being secured to the shaft at -point 9, while the lower end is secured to tubular 'member 2 at a point 9a. Thus, spring 8 will resist rotation of the `fan and the shaft in either direction and will tend Vto return andfkeep them to a normal position of rest. The fan blades -are `set at an angle of approximately thirty-five degrees so that when -air flows up past the fan blade, -it will rotate so as to advance the fan and its shaft in an upper direction. The upper end of this shaft lpushes against a vlever bar I0. The shaft raises the right hand end of lever bar Ill which is 4provided with a fulcrum orpivot point II, comprising a pin I2 and actuates the contacts Aof micro switch I4, by pressing against switch actuating pin I3, the characteristic of this micro switch being such that a motion of only .001 -of its actuating pin is necesary to open or close its contacts. The fulcrum point II of lever .I0 can be raised or lowered slightly by virtue of the fact that its -pin is mounted eccentric within its support I5, this eccentricity being approximately that of the order of .010. Pin support I5 is secured to an indicati-ng pointer I6 which is pivoted on the outside of the casi-ng by means of a rivet il, a lock screw I8 being provided to hold the pointer in a desired position. When lock screw I8 is released and the pointer moved, the fulcrum point II is moved up or down and this in turn readjusts the pointer at which shaft 4 will lactuate the vmicro switch. To keep out dust vand moisture, acover I9 is provided and is secured by Aany suitable means such as screws 20, also, the under side of casing I is provided with a lock nut 2I to securely hold the tubular member 2 in position.

In the operation of this device, when air flows past the fan it rotates and winds up the spring to a degree just sufcient to resist the torque of the air flowing on the fan 5. When the air velocity has reached a suitable predetermined value, the fan will have rotated to such a point that the micro switch which controls a circuit of a radio transmitter closes. Should the air flow fall below this value, the micro switch will open again. The air flow necessary to open or close the micro switch can be set as required by means of the eccentric support pin l5.

This device is particularly adapted for use with cooling devices for vacuum tubes of a radio transmitter, such as disclosed inFinch Patent #2,176,- 657, patented October 17, 1939, and specifically as is shown in Fig. 5 and described below in Vthis specification. The contacts IS and shown in Fig. 1 of the above mentioned Finch patent are so connected in the electrical circuit that the power will be removed from the thermionic tube in case of failure of the cooling air or inthe case of an excess temperature due to any cause. Y The latter contacts are to be omitted and in their place the device of this invention is employed, the circuit connections being broken by the micro switch i4. Y

Referring now in detail to Fig. 5, of this application, `the enclosing duct d0 is arrangedv to be supplied by cooling air flowing in the direction indicated by arrows di from an air filter (not shown), the air being discharged from the'i'llter directlyvin the duct 43 which can be arranged to carry the air to the outside atmosphere, as indicated by arrows 42, if the radio apparatus is located within a building. Within the container there is located a metal supporting member d3 which supports a solid metallic block 44 having a tapered aperture therein for securing thereto an anode d5 of a thermionic tube d6 of a radio transmitter having filament leads-4l and grid lead d8, the tube 45 being clamped to member 44 by means of a clamping device 49. Directly above tube l5 there is arrangeda fan 55 driven -by a motor 5| which forces air around the anode @5. In order that the air may be properly controlled, an air flow interlock of this invention, asV indicated by 52, is supportedeby a bracket 53 with its fan end 5 pointed downward. The'shaft should be set at an angle of about thirty degrees with the vertical, in order that `it will be parallel to the air flow. This is because the fan imparts rotary motion to the air iloW,` in addition to imparting vertical Inotion. The device should be set to close the switch I4 at an Yair flow just below the normal flow. Then,any material reduction in the air flow, such. as might be caused by a stoppage` of the space betweenthe cooling ns or the stoppage of the air lter placedl in the air screen,` would allow the fan to rotate backwards and thus cause the switch contacts to open. f .It so happens thatlwhen the air Vilow in a deviceas shown in Fig. 5 is restricted, the rotary motion of the air at the interlock device becomes greater relative to the vertical'motion resulting in a change in direction. This change in direction of air flow decreases the torque exerted on the fan blades and thus accentuates the effect obtained by the decrease in air now. The location of the fan, of the iiow interlock device and the -direction of the pitch of this fan is so chosen as to obtain maximum Vadvantage of this effect.

In addition to the air ow interlock 52, there is provided a thermostat element indicated as 3l, which is provided with a cord 32, terminating in a snap switch 33 having a spring 34, the spring being arranged so as to maintain switch 33 under tension and in the normal operation position contacts 35 and 3B are closed by switch blade 33. By means of this additional thermostatic arrangement, the electrical contacts are essentially at ground potential, while the actuating thermostat element is subjected to the anode potential of the radio transmitter.

In Fig. 6, the air flow interlock 52 is arranged '.just outside the intake manifold of a blower 55 with its fan 5 located approximately in the center of the blower, and is secured to blower 55 by means of a supporting bracket 56, the blower 55 being driven by any suitable means, such as an electric motor 51. The outlet manifold 58 is connected to any device to be cooled, the air flow of which is controlled by means of leads 59 operated by switch contacts M.

1 A modification of the device of this invention described above is shown in Fig. 4 wherein the fan Yis made of rather heavy metal or, if ded sired, a metal ring 23 may beplaced around fan 5 soV as to increase its inertia and make it respond more slowly to change in the air flow. Also, other mechanisms may be used Yto'cause the rotation of the fan to actuate the switch or for adjusting the point at which the spring contacts operate. Furthermore, an indicator can be added to this device for indicating the amount of air iiow. Therefore, this invention should not be limited to the precise device as shown.

What is claimed is: Y v

1. ,An air ow interlock comprising a rotatable shaft, a multi-blade fan located at one end of saidshaft, the axis of said shaft and said fan being located parallel toa iiow of air, a spring member applying a desired torque to said shaft, an electric switch mounted at the other end of said' shaft and having contacts, means for providing a quick closing and opening of said contacts when said fan rotates to predetermined positions. 1

2. An air iiow interlock comprising av tubular housing portion, a fan mounted upon a shaft coaxial with said housing portion, a helical spring located Within said tubular housing portion and arranged coaxial with said shaft to resist rotational motion lofsaid fan, and electrical contacts, means for closing and opening said contacts to control circuit connections when said f an rotates to predetermined positions.

3. An air flow interlock comprising a rotatable shaft, a fan mounted on one end of said shaft, the other endv of said shaft being threaded so that the shaft advances along its axis with rotation of said fan, and means for actuating electrical' contacts when said shaft advances a predetermined amount by rotation of said fan.

4. An air flow interlock comprising a rotatable shaft, afan mounted on one end of said shaft, the, other end of said shaft being threaded so that the shaft advances along its axis with rotation of said fan, means for actuating welectrical contacts when said shaft advances a predetermined amount by rotation of said fan, and means for adjusting theY point at which said contaacts open and close. 5. An air iiow interlock located to be responsive to a flow of air comprising a housing, a dpending tubular member supported by saidhousingr, a shaft located within and passing Vthrough said tubular member, a bearing for said shaft located at one end of said tubular member, a spring member1 located Within said tubular member and encircling said shaft and xed at one end thereof, the other end of said spring member secured to said tubular member to apply a desired torque to said shaft, a switch within said housing, an air responsive member located at one end of said shaft, and means interposed between said switch and an end of said shaft which is opposite said air responsive member to actuate said switch upon a predetermined velocity of air flow.

6. An air flow interlock located to be responsive to a fiow of air comprising a housing, a depending tubular member supported by said housing, a shaft located within and passing through said tubular member, a bearing for said shaft located at one end of said tubular member, a spring member located within said tubular member and encircling said shaft and fixed at one end thereof, the other end of said spring member secured to said tubular member to apply a desired torque to said shaft, a switch Within said housing, an air responsive member located at one end of said shaft, and means comprising a lever interposed between said switch and an end of said shaft which is opposite said air responsive member to actuate said switch upon a predetermined velocity of air flow.

7. An air flow interlock located to be responsive to a flow of air comprising a housing member, a graduated scale located on the outside of said housing, a depending tubular member supported by said housing, a shaft located within and passing through said tubular member, a bearing for said shaft located at one end of said tubular member, a spring member encircling said shaft and xed at one end thereof, the other end of said spring member secured to said tubular member to apply a desired torque to said shaft, a switch within said housing, an air responsive member located at one end of said shaft, means comprising a lever interposed between said switch and an end of said shaft which is opposite said air responsive member to actuate said switch upon a predetermined velocity of air flow, and an indicator member located near said graduated scale outside of said housing, a member joining said lever and said scale passing through an opening in said housing to indicate the velocity of the air flow.

8. An air flow interlock comprising a rotatable shaft, a fan mounted on one end of said shaft, the other end of said shaft being threaded so that the shaft advances along its axis with rotation of said fan, a switch member having electrical contacts located above said threaded portion of said shaft, a pivoted link member interposed between said switch member and said shaft to actuate said switch, a pivot member eccentrically mounted for pivoting said link member to adjust the point at which said switch contacts open and close.

9. An air flow interlock comprising a rotatable shaft, a multi-blade fan having a heavy ring member surrounding the outward portion of said fan blades to increase its inertia and make it respond more slowly to a change in the air flow, said fan being mounted on one end of said shaft, the other end of said shaft being threaded so that the shaft advances along its axis with rotation of said fan, and means for actuating electrical contacts when said fan advances a predetermined amount by rotation of said fan.

l0. An air fiow interlock comprising a housing mounted in close proximity to a blower, a depending tubular member secured to said housing, a shaft located within and passing through said tubular member and arranged parallel to the intake flow of air of said blower, a spring member located within said tubular member and encircling said shaft to apply a desired torque thereto, an electrical switch within said housing having contact means, and means for actuating said switch contacts when said fan rotates to a predetermined position.

11. An air iiow interlock comprising in combination a rotatable shaft, a multi-blade fan located at one end of said shaft, a spring member encircling said shaft to apply a desired torque to said shaft, an electric switch mounted at the other end of said shaft, means including a lever for actuating said switch when said fan rotates to a predetermined position, and means associated with said lever to adjust the position of said first mentioned means to vary the speed of opening and closing of said contacts.

12. An air floW interlock comprising a multiblade fan, a rotatable shaft for said fan, said shaft being mounted substantially parallel to a flow of air, a spring member attached to said shaft for applying a desired torque thereto, an electrical switch having electrical contacts, means cooperating with said shaft for actuating said switch, said fan being so rotated by the flow of air and its blade pitch being so determined with respect to said rotatable shaft that a change of the direction of the fan rotation due to the stoppage of the flow of air actuates said switch.

13. An air flow interlock comprising a rotatable shaft, a multi-blade fan mounted on one end of said shaft, the blades of said fan being set approximately thirty-five degrees with respect to its axis, the other end of said shaft being threaded with substantially forty turns per inch so that the shaft advances along its axis with rotation of said fan, and means for actuating electrical contacts when-said shaft advances a predetermined amount by rotation of said fan.

14. An air flow interlock comprising a housing having a threaded aperture therein, a rotatable shaft, a fan mounted on one end of said shaft, the other end of said shaft being threaded to run freely in said threaded aperture in the housing to cause said shaft to move axially when said fan is operated, and means actuated by the axial movement of said shaft for operating said switch.

JAMES L. FINCH, 

